1. Field of the Invention
The present invention relates to a general purpose loss-proof terminal for forming electric connections by clamping between two conducting elements such for example as an electric wire and a connection area of an electric apparatus.
2. Description of the Prior Art
It is generally known that, in the present state of the technique, there exist at least two main types of terminals for forming such connections.
The first type of terminal, generally called "stirrup" terminals, does not require any particular preparation of the end of the electric wire where the connection is to be made, unless it is simply bared in the case where the electric wire is covered with an insulating sheath. In this first type of terminal, the connecting area is disposed at the bottom of a recess formed in an insulating material body forming a guide cage, and has a tapped bore (or even a smooth bore at right angles to which is disposed a nut) in which is screwed a clamping screw equipped with a stirrup connection. Usually, this stirrup connection of a width essentially equal to that of the recess, is fitted so that it cannot be lost under the head of the screw (between head and screw thread). Thus, to make a connection with an electric wire, the screw is unscrewed then the end of the wire, bared if required, is introduced into the free gap between the connecting area and the stirrup connection. Then the screw is screwed up tight until the end of the wire is suitably compressed between the stirrup and the connecting plate. So that the assembly formed by the screw and its stirrup portion cannot be lost, the recess comprises, preferably at the level of the opening through which screwing up takes place, a narrowed portion which is either integrally molded therewith or formed by an added element such as a cap.
Thus, at the end of screwing out, the stirrup portion comes into abutment against the narrow portion of the recess and is thus blocked so that it cannot be lost.
The second type of terminal, generally called cage terminals, comprises a clamping cage open at least at one of its ends so as to allow a connecting tag or possibly the end of a wire to pass therethrough and a face having a tapped bore in which is screwed a screw; As before, this cage is mounted inside a recess formed in an insulating material body. So that the screw cannot be lost, this recess has, at the level of the opening through which screwing up takes place, a narrow portion in which the head of the screw comes into abutment at the end of screwing out.
It can be seen that these two types of terminals are not suitable for connecting wires equipped with closed connecting tags whose use is imposed by certain regulations and which have a hole through which the clamping screw must necessarily pass.
In fact, in the case of a stirrup terminal, it would be necessary, in order to fit the connecting tag, to previously remove the screw-stirrup assembly, which is incompatible with the loss proof nature of this fitting.
Moreover, the disadvantage of cage terminals comes from the fact that, because of stresses exerted during tightening of the screw, the cage must necessarily have relatively thick walls. Consequently, the width of the internal volume of the connecting tag and so the width of the tag used will be appreciably less than the width of the recess, which is usually imposed for reasons of space, in particular in the case where several identical terminals are juxtaposed. It is clear that the use of closed connecting tags in such terminals would be contrary to the spirit of the regulations which impose the use of closed connecting tags, for in the case of poor clamping, the connection is not properly held.